There is an increasing demand to reduce the sulfur content of hydrocarbonaceous oil to produce products which have very low concentrations of sulfur and are thereby marketable in the ever more demanding marketplace. With the increased environmental emphasis on the requirement for more environmentally friendly transportation fuels, those skilled in the art have sought to find feasible and economical techniques to reduce the sulfur content of hydrocarbonaceous oil to low concentrations.
Traditionally, hydrocarbons containing sulfur have been subjected to a catalytic hydrogenation zone to remove sulfur and produce hydrocarbons having lower concentrations of sulfur. Hydrogenation to remove sulfur is very successful for the removal of the sulfur from hydrocarbons that have sulfur components that are easily accessible to contact with the hydrogenation catalyst. However, the removal of sulfur components which are sterically hindered becomes exceedingly difficult and therefore the removal of sulfur components to a sulfur level below about 100 ppm is very costly by known current hydrotreating techniques. It is also known that a hydrocarbonaceous oil containing sulfur may be subjected to oxygenation to convert the hydrocarbonaceous sulfur compounds to compounds containing sulfur and oxygen, such as sulfoxide or sulfone for example, which have different chemical and physical characteristics.
Although the contrasting characteristics of hydrocarbons and the sulfoxides or sulfones would suggest the separation of the sulfur-oxidated compounds, there is a continuing need for a process to successfully isolate the sulfur-isolated compounds while maximizing the yield of sulfur-free hydrocarbons in a facile and economical manner. Fractionation of diesel boiling range hydrocarbons to isolate and recover sulfur-oxidated compounds is not possible because the sulfur-oxidated compounds boil within the same range as some of the diesel fraction. Adsorbents have a relatively low capacity on a weight basis and when large quantities of hydrocarbon feedstocks containing sulfur-oxidated compounds are to be separated, simple adsorption is not economically feasible.